The present invention relates to a semiconductor device that includes a CMOS transistor having a salicide structure, and more particularly it relates to a semiconductor device having a means for detecting a missing part in a high-melting-point metal silicide film in the connection part between an n-channel MOS transistor gate electrode and a p-channel MOS transistor gate electrode.
In recent years, with shrinking of the design rule for MOS transistors, because it has become essential to reduce the parasitic resistance associated with the gate electrode, MOS transistors having a salicide structure have come into focus. In these MOS transistors having a salicide structure, with advancements in the shrinking of the design rule, it has become difficult to form a high-melting-point silicide layer in a self-aligning manner on a polysilicon film pattern which serves as the gate electrode, and on a diffusion layer which serves as a source/drain region, and particularly, missing parts occur in the high-melting-point silicide film pattern and high-melting-point metal silicide layer.
A detection means for detecting such missing parts is one in which a detection element formed by a n+-type polysilicon film pattern of sufficient length or p+-type polysilicon film pattern and a high-melting-point metal silicide film pattern formed in self-aligning manner thereover so as to form a polycide interconnect pattern, or a detection element formed by a n+-type diffusion layer or p+-type diffusion layer of sufficient length over which a high-melting-point silicide layer is formed in self-aligning manner is used, the resistance of either of these detection elements being measured to perform detection of missing parts. If there is no missing part in the high-melting-point metal silicide film pattern or the high-melting-point metal silicide layer, the above-noted resistance value is a low value. For example, in the case in which there is a macro-level missing part having a length on the order of micron in the high-melting-point metal silicide film pattern or high-melting-point metal silicide layer, the above-noted resistance value is high.
For example, in the case of a CMOS transistor having a salicide structure, the inverter gate electrode is as follows. In the element-separation regions of both transistors, an n+-type polysilicon film pattern (forming an n-channel MOS transistor gate electrode) and a p+-type polysilicon film pattern (forming the p-channel MOS transistor gate electrode) are directly connected, and a high-melting-point metal silicide film pattern is formed in self-aligning manner over these polysilicon film patterns, so as to constitute a gate electrode of the inverter. A missing part in the high-melting-point metal silicide film pattern on the inverter gate electrode tends to occur at the joining point between the n+-type polysilicon film pattern and the p+-type polysilicon film pattern, and the length of this missing part is in the order of no more than sub-micron size. When this type of missing part occurs on this p+-n+ junction, because the existence of this p+-n+ junction causes an increase in resistance, thereby causes an increase in the inverter gate delay time.
However, in detecting a missing part in a high melting point metal silicide film using a detection element such as described above, because there is only a small increase in resistance value caused by the existence of a missing part having a length in the sub-micron order, this approach to detecting a missing part at the junction of a n+-type polysilicon film pattern and a p+-type polysilicon film pattern formed on the gate electrode of the inverter is not suitable.
Accordingly, it is an object of the present invention to provide a semiconductor device, which includes a high-melting-point metal silicide film missing part detection element capable of detecting a minute missing part in a high-melting-point metal silicide film of a polycide interconnect in a semiconductor device including a CMOS transistor of salicide structure.
In order to achieve the above-noted object, the present invention adopts the following basic technical constitution.
The first aspect of the present invention is a semiconductor device comprising an n-channel MOS transistor 1 and a p-channel MOS transistor 2 each having a salicide structure, and a high-melting point metal silicide film missing part detection element 3 detecting a missing part 128 formed in a high-melting point metal silicide film 126A provided on a gate electrode 106a, 106b of the MOS transistors 1,2, wherein the high-melting point metal silicide film missing part detection element 3 comprising a polysilicon film pattern 110 with alternate connection between an n-type region 116ab having a prescribed impurity concentration and a p-type region 116ba having a prescribed impurity concentration, and a high-melting point metal silicide film 126A formed on the polysilicon film pattern 110.
In the second aspect of the present invention, the impurity concentration of the p-type region is higher than that of the n-type region.
In the third aspect of the present invention, both ends of the polysilicon film pattern are made of the p-type region.
In the fourth aspect of the present invention, the impurity concentration of the n-type region is higher than that of the p-type region.
In the fifth aspect of the present invention, both ends of the polysilicon film pattern are made of the n-type region.
In the sixth aspect of the present invention, a source/drain region of the MOS transistor is formed by a LDD region and a source/drain diffusion layer having an impurity concentration higher than that of the LDD region, an impurity concentration of n-type region of the high-melting point metal silicide film missing part detection element is equal to that of the source/drain diffusion layer of the n-channel MOS transistor, and an impurity concentration of p-type region of the high-melting point metal silicide film missing part detection element is equal to that of the source/drain diffusion layer of the p-channel MOS transistor.
In the seventh aspect of the present invention, a source/drain region of the MOS transistor is formed by a LDD region and a source/drain diffusion layer having an impurity concentration higher than that of the LDD region, an impurity concentration of n-type region of the high-melting point metal silicide film missing part detection element is equal to that of the LDD region of the n-channel MOS transistor.
In the eighth aspect of the present invention, a source/drain region of the MOS transistor is formed by a LDD region and a source/drain diffusion layer having an impurity concentration higher than that of the LDD region, an impurity concentration of p-type region of the high-melting point metal silicide film missing part detection element is equal to that of the LDD region of the p-channel MOS transistor.
In the ninth aspect of the present invention, minimum line width of the polysilicon film pattern of the high-melting point metal silicide film missing part detection element is equal to a gate length of a gate electrode of the MOS transistor.
In the tenth aspect of the present invention, the high-melting point metal is either one of titanium or cobalt.